Given a binary tree, flatten it to a linked list in-place.
For example,
Given
1
/ \
2 5
/ \ \
3 4 6
The flattened tree should look like:
1
\
2
\
3
\
4
\
5
\
6
Hints:
If you notice carefully in the flattened tree, each node's right child points to the next node of a pre-order traversal.
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
void flatten(TreeNode* root) {
TreeNode* now = root;
while (now){
if (now->left){
TreeNode* pre = now->left;
while (pre->right){
pre = pre->right;
}
//将当前节点的右孩子连接到当前节点左孩子的的最右孩子
pre->right = now->right;
//当前节点的左孩子变为右孩子，左孩子置为NULL
now->right = now->left;
now->left = NULL;
}
now = now->right;
}
}
};
